Wednesday, March 20, 2013

Redistribution facts

1. When redistributing something (for example, EIGRP into BGP) with route-maps, changes in access-list that used to match specific routes, do not force new routes to automatically populate BGP table! For this to happen, we have to "no redistribute eigrp X ......" and then re-enter it!

More to come :)

Redistribution of static routes to EIGRP

I have learnt an interesting fact about redistribution into EIGRP process. If you want to redistribute static route as INTERNAL to EIGRP, you should use simple network x.x.x.x command instead of redistribute static. EIGRP treats static routes to interface as a connected networks, so it works pretty well!

eBGP connection issues

eBGP connections differ form iBGP connections in the way router with TTL value inside the IP packet. By default, BGP sends packets with TTL value set to 255 to it's iBGP peers, so if we are connecting to the loopback interface (or other IP addresses that are more than 1 hop away) everything works well out of the box. This is not the case for the eBGP peers. In order to connect to loopback interface of eBGP peer, we have to configure "neighbor x.x.x.x ebgp-multihop 'TTL value'" router command, because by default BGP sends packets with IP TTL set to 1! If you forgot to do this this, "show ip bgp summary" will show the neighbor connection sitting in IDLE state!

Thursday, March 7, 2013

How to delete Local SR on XenServer

1. First, you have to determine the Storage-Repository-UUID:

xe sr-list 

2. Find the corresponding Physical Block Device (PBD):

xe pbd-list sr-uuid=your-SR-uuid

3. Unplug the PBD:

xe pbd-unplug uuid=your-PBD-uuid

4. Delete PBD:

xe pbd-destroy uuid=your-PBD-uuid

5. Delete the association of your SR and the PBD:

xe sr-forget uuid=your-SR-uuid

P.S. Thanks to Citrix Forum